Lecture 1 Flashcards
Avian characteristics
- reflect flight requirements (but not all birds fly, and bats do)
- Feathers
- Skeleton-reduction and fusion (vertebral column, forelimbs, pectoral and pelvic girdle); pneumatic bones, fusion and elimination of bones, pneumatization of bones (but dneser), more genes associated with ossification than in mammals
- Furcula-fused clavicle
- Vertebral column- most posterior vertebrae fused together, pelvis expanded
- Ribs-
- Keeled sternum-not all
- Pygostyle-fused caudal vertebrae
- Wings-fusion and reduction
- Hindlimbs-Tibiotarsus and tarsus-metatarsus
- Skull-no teeth
- Large braincase (large eye sockets), brain structure- seat of learning
- Respiration-lungs and air sacs, 4 chm heart, oviparous
- Eggs-endothermy-no live births
Shared avian and reptilian characteristics
- All are Diapsid-Sauropsid
- Single middle ear bone=columella
- Multiple bones in lower jaw
- Articulate/quadrate joint
- Single occipital condyle (mammals have 2)
- Large yolked egg
Phylogenetic position
- Chordata-dorsal hollow nerve cord, notochord, postanal tail, pharyngeal gill slits
- Vertebrata/Craniata- vertebrae (or arcualia), canium + tripartite brain most closely related to eurchordata, plus genetic and developmental features.
- Amniotic Vertebrate-extraembryonic membranes, yolk, amniotic cavity, aminion, allantois, chorion, shell
- Diapsud (two temporal openings)- Sauropsid (lung structure)
- Archosauria- antorbital fenestra=hole in front of eyes
- Common ancestor with Archosaurs
- Theodont or theropod?-long rancorous debate
Thomas H. Huxley
1860’s recognized similarities between Archaopteryx and theropod dinosaurs. Campsognathus- proposed theropod common ancestor-too little evidence
Gerhard Heilman
1926- “The origin of Birds”-discounted similarities as convergence
John Ostrom
1964-Too many similarities for convergence (wrist half moon shape, claw on hind foot)
Allan Feduccia/Larry Martin
1980s-present: advocate theodont
Current
Birds included in dinosaur clade
What features determine that birds share a common ancestor with Dinosaurs
a. Dinosauria-hole in hip; bipedial
b. Dinosauria-Saurischian- pelvis with three radiating bones
(New phylogeny proposed)
Chordata
pharyngeal gill slits, post-anal tail, dorsal hollow nerve cord, notochord
Vertebrata/Craniata
- vertebrae (or arcualia), cranium/tripartite brain, closely related to euchordata, genetic and developmental features
Amniotic vertebrate
-extraembryonic membrane, yolk, amniotic cavity, amnion, allantois, chorion, shell
Diapsid
-two temporal openings
Sauropsid
-Lung structurea
Archosauria vertebrates
- anteorbital fenestra- hole in front of eye